1. Field of the Invention
The invention relates to a system for providing verified information exchange between an electronic information carrier and a read/write unit for reading and writing in the information carrier.
The invention likewise relates to an information carrier and a read/write unit to be used in such a system.
2. Description of the Related Art
Systems of this type may be used, for example, for access control n hotels, the information carrier serving as a key to a room and having a further possibility of containing additional information (for example, validity) which is to be read out by a read/write unit which is also capable of writing information on the carrier. This type of information may refer, for example, to use of hotel facilities for which a fee is to be paid, so that it may be used for computing the amount to be settled on departure.
The information exchange between the information carrier and the read/write unit could be realised by means of metal-to-metal contacts. However, this is undesirable because fouling or oxidation of metal-to-metal contacts may occur and these contacts may give rise to fraud.
Alternatively, it is possible to provide information exchange without metal-to-metal contacts. It may be by digital data transmission which is generally effected bit serially. It is then necessary to monitor whether there is any error in transmission of the data from the read/write unit to the information carrier. It is conceivable for monitoring of the data integrity to be carried out by performing a read cycle of the information carrier following each write cycle carrier, and in case a bit error is detected to repeat the write and read cycles. However, this manner of checking is time-consuming and may therefore lead to an undesirable interruption of the information exchange if, as is customary the information carrier is quickly inserted and removed from the read/write unit.